To provide anesthesia to a patient during surgery, an anesthesia system is employed that includes a plurality of components. The primary component is an anesthesia machine, that regulates the flow of anesthesia gas and air to and from the patient. A carbon dioxide absorber may be attached to the anesthesia machine to remove carbon dioxide from the exhaled breath of the patient in a rebreathing circuit.
On the patient end, a face mask or an endo-tracheal tube is provided that can be coupled to the patient for delivering gas to the patient. Examples of face masks can be viewed at the assignee's web-site, www.KingSystems.com, or in Hinkle U.S. Pat. No. 4,896,666. Examples of tracheal tubes are shown in Frasse, U.S. Pat. No. 5,499,625; and Bertram, U.S. Pat. No. 5,819,733. These patient-coupled devices (the face mask and/or the endo-tracheal tube) are connected to the anesthesia machine in fluid (gaseous) communication via a breathing circuit that extends between the patient-coupled devices and anesthesia machine.
Several different types of breathing circuits exist. Two primary types of breathing circuits are dual limb circuits and unilimb circuits.
Dual limb circuits comprise a pair of separated tubes that include an inspiratory tube for delivering gas from the anesthesia machine to the patient, and an expiratory tube that delivers exhaled gas from the patient to the anesthesia machine. In a dual limb circuit, the two tubes comprise separate tubes that, at the patient end are typically fluidly coupled together by a “Y” or “T” tube. The machine ends of the tubes of a unilimb circuit are separate, with the machine end of the inspiratory tube being connected to the “outflow” port of the anesthesia machine, and the machine end of the expiratory tube being connected to the “inflow” port of the anesthesia machine. An example of a schematic representation of a dual-limb circuit can be seen in FIG. 1c of Fukunaga et al., Published U.S. Patent Application No. US2003/0183232A1 (2 Oct. 2003).
The second type of circuit is a unilimb circuit, wherein inspiratory tube are joined together. An example of a unilimb breathing circuit is shown in Leagre et al., U.S. Pat. No. 5,404,873; Fukunaga, U.S. Pat. No. 4,265,235 and Fukunaga et al, U.S. Pat. Nos. 5,778,872; 5,983,891; 5,983,894; 5,983,896; 6,003,511; 6,564,799; Fukunaga et al, Published U.S. Patent Applications Nos 2003/0075176 and US2003/0183231; and Sikora, U.S. Pat. No. 5,121,746.
As best shown in the Leagre '873 patent, a unilimb circuit typically includes a relatively rigid machine end (proximal) connector through which the circuit is coupled to an anesthesia machine; and a relatively rigid patient end (distal) connector that can be coupled to a face mask or tracheal tube, for coupling the breathing circuit to a patient. A relatively flexible expiratory tube extends between the patient end connector and the machine end connector. A relatively flexible, inspiratory tube is disposed co-axially with the expiratory tube. To promote better heat exchange to warm inspiratory gasses, the inspiratory tube typically has a smaller diameter than the relatively larger diameter expiratory tube so that the inspiratory tube can reside internally of the expiratory tube. The breathing circuit shown in the Leagre et al., '873 patent is sold commercially by the Assignee of the instant application, KING SYSTEMS CORPORATION, under the trademark of the UNIVERSAL F® breathing circuit.
Other breathing circuits sold by the Assignee of the present invention, KING SYSTEMS CORPORATION are shown, at least schematically, in the Fukunaga et al., '872; '894; 896; '511; and '799 patents discussed above.
The breathing circuits illustrated in the Fukunaga and Leagre patents are drawn as unilimb breathing circuits wherein the expiratory and inspiratory tubes are disposed co-axially with each other. Typically, the inner, relatively smaller diameter tube is used as an inspiratory tube, and the outer, relatively larger diameter tube is employed as the expiratory tube. A noteworthy difference between the breathing circuit shown in the Leagre patent and those shown in the Fukunaga patents resides in the differences in the machine end couplers of the circuits.
The inspiratory and expiratory tube of the Leagre and Fukunaga devices, as embodied in the UNIVERSAL F® and UNIVERSAL F2® are similar, as both employ a corrugated inspiratory tube and a corrugated expiratory tube. The corrugated inspiratory tubes and corrugated expiratory tubes are corrugated to have a single rest length, while permitting the length of the tube to be expanded, or contracted.
The variability of the length of the corrugated inspiratory and expiratory tubes is engineered into the UNIVERSAL F® and UNIVERSAL F1® circuits, to permit the length of the tubes to be stretched (lengthened) and compressed (shortened) for short periods of time. This variation in length often occurs when the relative position of the patient and the anesthesia machine is changed, and usually involves the need to stretch the tube during this change in relative position. However, as the expiratory and inspiratory tubes are designed to have a fixed rest length, any change in the length of the inspiratory and expiratory tubes from their fixed rest length exerts “stress” on the expiratory tubes, and causes the expiratory tube to exert either a compressive or an expansive force, (as appropriate) to enable the tube to return back to its unitary rest length.
During the stretching of the expiratory tube, the inspiratory tube typically does not stretch as it is only connected to the machine end connector in the UNIVERSAL F® and UNIVERSAL F2® breathing circuits. However, both the inspiratory and expiratory tubes are likely to stretch in breathing circuits such as one sold by Meridian Medical Systems, as the Meridian Medical breathing circuit employs an the inspiratory tube that is connected to both the machine end and patient end connectors.
Another reason for employing single rest length corrugated tubes is to prevent the tubes from becoming kinked. It is highly desirable to prevent such kinking, because such kinking can result in the obstruction or blockage of flow of gas in the tube, in much the same way that the flow of water is obstructed or blocked through a garden hose when it becomes kinked.
Another unilimb breathing circuit is shown in Sikora, U.S. Pat. No. 5,121,746. The Sikora device employs a unilimb circuit, wherein an expiratory and inspiratory tube are joined at a common wall, to give the breathing circuit a θ like configuration. The tubing shown in the Sikora patent also appears to be corrugated, no doubt, for many of the same reasons as a corrugated tube is employed in the UNIVERSAL F® and UNIVERSAL F2® devices described above.
Although the devices described above, and in particular the UNIVERSAL F® and UNIVERSAL F2® devices perform their intended functions quite admirably, room for improvements exists.
One source of difficulties resides in the unitary rest length of the breathing circuit the unitary rest length requires multiple lengths of tubing to be manufactured, to accommodate different situations and preferences. Some medical professionals prefer relatively shorter (e.g. 44 inch, 112 cm) length tubes, whereas other medical professionals prefer to move the anesthesia machine further away from the patient so that it is less obtrusive, thereby requiring relatively longer (e.g. 88 inch, 224 cm) breathing circuits.
From a manufacturer's standpoint, this desire for different circuit lengths requires the manufacturer to manufacture breathing circuits in a variety of lengths. From the viewpoint of a user (e.g. hospital or surgical center), these different desired lengths require the end user to inventory several different circuit lengths.
Another difficulty is encountered in shipping. Because unitary rest length circuits using corrugated tubing have a single rest length, the tube must normally be sized to have a relatively long (e.g. 44 or 88 inches; 112 or 224 cm) rest length, so that when the device is in use, it is long enough to serve its purpose while being neither stretched nor compressed. Because of the elasticity of the single rest length corrugated tube, the tubing when stretched exerts a compressive force, that tends to compressively shorten the tube back to its rest length.
It is not recommended that the device be used when stretched, as the compressive force exerted by the tube can help facilitate both external disconnects, wherein the breathing circuit is pulled away from its coupling to either the machine or the patient; or internal disconnects wherein the corrugated breathing tubing is pulled away from one of the machine or patient end couplings. It is desirable to avoid both internal and external disconnect inducing situations.
As a result of this, a 44 inch (112 cm) breathing circuit, for example, has a 44 inch (112 cm) rest length that ordinarily cannot be compressed (and thereby made smaller for shipping) for any significant length of time without the exertion of an external clamping force. The inability to change the rest length to shorten it, without the imposition of external clamping forces, requires the manufacturer to provide enough storage space in a container or box, to accommodate the entire 44 inch (112 cm) length of the hypothetical 44 inch (112 cm) breathing tube. Additionally, it requires the hospital or surgical center user to provide storage space sufficient to accommodate the entire 44 inch (112 cm) length of the breathing circuit.
From the foregoing discussion, it will be appreciated that it would be desirable to have a breathing circuit, that could be compressed, to take up less space during shipment. Additionally, it would be desirable to construct a breathing circuit including a plurality of sustainable rest lengths, so that, for example, a single device could be extended from its fully compressed (shipment) length, to, for example, a partially extended “short tube length” having an overall length of about 44 inches (112 cm), and stretched further into a fully extended (fully decompressed) position wherein it would have a rest length equal to that of a longer breathing circuit, such as an 88 inch (224 cm) breathing circuit.
One object of the present invention is to provide such a breathing circuit having a plurality of fixed rest lengths, so that the device can be placed in a fully compressed position, to reduce the length for shipping, storage and some anesthesia applications, but also be extended, and sustainably be maintained in a plurality of extended rest length positions, to provide a desired greater length than the compressed position. Preferably, the device is also sustainable in a variety of rest lengths that vary in length between the fully compressed position and the fully extended position of the breathing circuit.